Field
The present disclosure generally relates to devices and methods for repairing bone fractures, and more specifically to improved flexible bone screw devices and methods.
Description of the Related Art
Surgical techniques for the treatment of bone fractures commonly known and used in the art include external fixation, pinning, and joint replacement. In some situations, each of these techniques can be inadequate for facilitating satisfactory recover of the bone fracture. A proximal humerus fracture, i.e., a fracture of the humerus near the humeral head, is one such case. Replacement of the shoulder joint with a prosthesis is a complex and invasive procedure that can lead to the death of elderly patients, for whom proximal humerus fractures are common. Similarly, internal fixation of a proximal humerus fracture with one or more humeral plates and bone screws may successfully maintain the correct position of the humerus fragments, but the extensive dissection of soft tissue that is an integral part of this approach leads to high morbidity.
In light of the above, flexible bone screws have been developed for treatment of certain fractures, such as the percutaneous fixation of softer bone tissue to stronger bone tissue. For example, in a proximal humerus fracture, one or more flexible bone screws can be employed to fix the cancellous bone of the humeral head to the cortical bone of the humerus bone shaft. Specifically, a flexible bone screw is introduced into the intramedullary cavity of a humerus through an opening in the antero-lateral cortex on a first side of the humerus. The flexible bone screw is then advanced, via rotation, into the intramedullary cavity along an interior surface of the cortex on a second side of the humerus, and threaded into the subchondral bone of the humeral head.
When initially advanced into the intramedullary cavity, threads at the tip of the flexible bone screw typically contact an interior surface of the cortex at some angle of incidence. Rotation of the flexible bone screw and contact between the threads and the interior surface of the cortex then cause the bone screw to move along the interior surface of the cortex toward the humeral head. Thus, during installation, the flexible bone screw undergoes significant bending while being rotated, similar to that experienced by a material sample undergoing a rotating beam test. As a result, the bone screw can subject to significant fatigue during a normal installation procedure, and plastically deform, heat, or even fail during the installation, each of which is highly undesirable.
Accordingly, there is a need in the art for a flexible bone screw capable of bending during rotation.